U.S. patent number 9,584,997 [Application Number 14/550,307] was granted by the patent office on 2017-02-28 for d2d device discovery method and apparatus based on lte cellular communications system.
This patent grant is currently assigned to Huawei Technologies Co., Ltd.. The grantee listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Shulan Feng, Han Zhou.
United States Patent |
9,584,997 |
Zhou , et al. |
February 28, 2017 |
D2D device discovery method and apparatus based on LTE cellular
communications system
Abstract
This invention is applicable to the field of communications
technologies, and provides a device to device (D2D) discovery
method and a first D2D user equipment (UE). The method includes:
the first D2D UE acquires timing information of the first D2D UE
from a Lont Term Evolution (LTE) cellular communications system;
receives in a discovery subframe, a device discovery signal from a
second D2D UE according to the timing information, wherein the
device discovery signal comprises a pilot orthogonal frequency
division multiplexing (OFDM) symbol and a device information OFDM
symbol; acquires an arrival time of the device discovery signal by
performing a time domain correlation of the pilot OFDM symbol of
the device discovery signal and a local pilot sequence, acquires
device information of the second D2D UE by parsing the device
information OFDM symbol of the device discovery. This invention
enables a D2D UE to effectively discover other D2D UEs, improves
system efficiency, and saves power of the D2D UE.
Inventors: |
Zhou; Han (Beijing,
CN), Feng; Shulan (Beijing, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen, Guangdong |
N/A |
CN |
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Assignee: |
Huawei Technologies Co., Ltd.
(Shenzhen, CN)
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Family
ID: |
49623050 |
Appl.
No.: |
14/550,307 |
Filed: |
November 21, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150078466 A1 |
Mar 19, 2015 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2012/082960 |
Oct 15, 2012 |
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Foreign Application Priority Data
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May 23, 2012 [CN] |
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2012 1 0162246 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
56/004 (20130101); H04W 76/14 (20180201); H04L
27/2601 (20130101); H04W 40/246 (20130101); H04L
5/003 (20130101); H04B 17/16 (20150115); H04W
8/005 (20130101); Y02D 70/21 (20180101); Y02D
70/142 (20180101); Y02D 70/1262 (20180101); Y02D
70/144 (20180101); Y02D 70/122 (20180101); Y02D
30/70 (20200801) |
Current International
Class: |
H04B
1/38 (20150101); H04L 27/26 (20060101); H04W
76/02 (20090101); H04W 56/00 (20090101); H04W
40/24 (20090101); H04B 1/40 (20150101); H04W
8/00 (20090101); H04B 17/16 (20150101); H04L
5/00 (20060101) |
Field of
Search: |
;375/219 ;455/73 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101771615 |
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Jul 2010 |
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CN |
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2 015 485 |
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Jan 2009 |
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EP |
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WO 2011/080533 |
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Jul 2011 |
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WO |
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WO 2011/161560 |
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Dec 2011 |
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WO |
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Other References
"Study on LTE Device to Device Discovery and Communication-Service
and System Aspects", 3GPP TSG SA Plenary Meeting #52, Jun. 6-8,
2011, 5 pages. cited by applicant .
"Operation Managed and Operator Assisted D2D", Intel, 3GPP TSG-SA
WG1 Meeting #57, Feb. 13-17, 2012, 4 pages. cited by
applicant.
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Primary Examiner: Washburn; Daniel
Assistant Examiner: Hassan; Sarah
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Application No.
PCT/CN2012/082960, filed on Oct. 15, 2012, which claims priority to
Chinese Patent Application No. 201210162246.X, filed on May 23,
2012, both of which are hereby incorporated by reference in their
entireties.
Claims
What is claimed is:
1. A discovery method in a device to device (D2D) communications
system, comprising: acquiring, by a first D2D user equipment (UE),
timing information of the first D2D UE from a Long Term Evolution
(LTE) cellular communications system; receiving, by the first D2D
UE in a first discovery subframe, a device discovery signal from a
second D2D UE according to the timing information, and the device
discovery signal comprises a pilot orthogonal frequency division
multiplexing (OFDM) symbol and a device information OFDM symbol;
and acquiring, by the first D2D UE, an arrival time of the device
discovery signal sent by the second D2D UE by performing a time
domain correlation of the pilot OFDM symbol of the device discovery
signal received in the first discovery subframe and a local pilot
sequence, and acquiring device information of the second D2D UE by
parsing the device information OFDM symbol of the device discovery
signal received in the first discovery subframe; wherein the first
discovery subframe comprises 14 OFDM symbols, and a frame structure
of the first discovery subframe comprises: every seven OFDM symbols
of the first discovery subframe are divided into one group, and, in
each group, any one symbol among the second symbol to the sixth
symbol is a pilot OFDM symbol and other six OFDM symbols are device
information OFDM symbols.
2. The method according to claim 1, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols is divided into M frequency resource elements in a
frequency domain, wherein M is an integer greater than or equal to
1; and one or more frequency resource elements of each OFDM symbol
serve as a device discovery resource element, and one or more of
the device discovery resource elements are selected by each D2D UE
as a carrier for a device discovery signal of the each D2D UE.
3. The method according to claim 1, wherein, when the timing
information is uplink timing information or downlink timing
information, receiving, by the first D2D UE in the first discovery
subframe, the device discovery signal from the second D2D UE
according to the timing information comprises: receiving, by the
first D2D UE in the first discovery subframe, the device discovery
signal from the second D2D UE according to the uplink timing
information or the downlink timing information of the first D2D
UE.
4. The method according to claim 1, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols comprises a cyclic prefix (CP), and a guard interval
(GI) is added to the first discovery subframe, wherein the GI is
located between the first discovery subframe and an adjacent paging
subframe following the first discovery subframe, and the length of
the CP of the first discovery subframe is determined according to
the GI.
5. The method according to claim 1, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols comprises a cyclic prefix (CP), wherein: both the
first discovery subframe and an adjacent paging subframe following
the first discovery subframe use normal CPs or extended CPs.
6. The method according to claim 1, wherein the method further
comprises: sending, by the first D2D UE, a device discovery signal
to the second D2D UE in a second discovery subframe according to
the timing information, so that the second D2D UE receives, in the
second discovery subframe, the device discovery signal sent by the
first D2D UE, performs a time domain correlation of a pilot OFDM
symbol of the device discovery signal received hi the second
discovery subframe and a local pilot sequence, to acquire an
arrival time of the device discovery signal sent by the first D2D
UE, parses a device information OFDM symbol of the device discovery
signal received in the second discovery subframe, to acquire device
information of the first D2D UE.
7. The method according to claim 1, wherein the method further
comprises: calculating, by the first D2D UE, a time at which a
signal is sent to the second D2D UE, according to the acquired
arrival time of the device discovery signal sent by the second D2D
UE and the device information of the second device.
8. A device to device (D2D) user equipment (UE), comprising: a
processor, configured to acquire timing information of the D2D UE
from a Long Term Evolution (LTE) cellular communications system; a
receiver, configured to receive, in a first discovery subframe, a
device discovery signal from a second D2D UE according to the
timing information, and the device discovery signal comprises a
pilot orthogonal frequency division multiplexing (OFDM) symbol and
a device information OFDM symbol; and the processor is further
configured to: acquire an arrival time of the device discovery
signal sent by the second D2D UE by performing a time domain
correlation of the pilot OFDM symbol of the device discovery signal
received in the first discovery subframe and a local pilot
sequence, and acquire device information of the second D2D UE by
parsing the device information OFDM symbol of the device discovery
signal received in the first discovery subframe; wherein the first
discovery subframe comprises 14 OFDM symbols, and a frame structure
of the first discovery subframe comprises: every seven OFDM symbols
of the first discovery subframe are divided into one group, and, in
each group, any one symbol among the second symbol to the sixth
symbol is a pilot OFDM symbol and other six OFDM symbols are device
information OFDM symbols.
9. The D2D UE according to claim 8, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols is divided into M frequency resource elements in a
frequency domain, wherein M is an integer greater than or equal to
1; and one or more frequency resource elements of each OFDM symbol
serve as a device discovery resource element, and one or more of
the device discovery resource elements are selected by each D2D UE
as a carrier for a device discovery signal of the each D2D UE.
10. The D2D UE according to claim 8, wherein, when the timing
information is uplink timing or downlink timing, the receiver is
configured to receive, in the first discovery subframe, the device
discovery signal from the second D2D UE according to the uplink
timing or the downlink timing of the D2D UE.
11. The D2D UE according to claim 8, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols comprises a cyclic prefix (CP), and a guard interval
(GI) is added to the first discovery subframe, wherein the GI is
located between the first discovery subframe and an adjacent paging
subframe following the first discovery subframe, and the length of
the CP of the first discovery subframe is determined according to
the GI.
12. The D2D UE according to claim 8, wherein the first discovery
subframe comprises a plurality of OFDM symbols, and each of the
OFDM symbols comprises a cyclic prefix (CP), wherein: both the
first discovery subframe and an adjacent paging subframe following
the first discovery subframe use normal CPs or extended CPs.
13. The D2D UE according to claim 8, wherein the D2D UE further
comprises a transmitter, configured to send a device discovery
signal to the second D2D UE in a second discovery subframe
according to the timing information, so that the second D2D UE
receives, in the second discovery subframe, the device discovery
signal sent by the D2D UE, performs a time domain correlation of a
pilot OFDM symbol of the device discovery signal received in the
second discovery subframe and a local pilot sequence, to acquire an
arrival time of the device discovery signal sent by the D2D UE,
parses a device information OFDM symbol of the device discovery
signal received in the second discovery subframe, to acquire device
information of the D2D UE.
14. The D2D UE according to claim 13, wherein, when the timing
information is uplink timing or downlink timing, the transmitter is
configured to send the device discovery signal to the second D2D UE
in the second discovery subframe according to the uplink timing or
the downlink timing of the D2D UE.
Description
TECHNICAL FIELD
The present invention relates to the field of communications
technologies, and in particular, to a D2D device discovery method
and apparatus based on a Long Term Evolution (Long Term Evolution,
LTE) cellular communications system.
BACKGROUND
In the last two decades, radio communications technologies have
developed enormously and the radio communications technologies are
emerging continuously. Radio communications networks increasingly
occupy people's lives by virtue of its enormous flexibility, and
become an indispensable part of people's lives.
However, radio spectrum resources are limited. With a sharp
increase of persons who use the radio communications networks and
with increasingly higher requirements on performance of the radio
communications networks, a shortage of spectrum resources has
become a key limitation on radio communication performance.
Currently, a cellular network is a prevailing radio communications
network. In this communication network, communication between two
terminals needs to be forwarded by a base station, and a same
packet, which is transmitted from a terminal to a base station and
then from the base station to the terminal, occupies an air
interface resource twice. If the two communications terminals are
in a relatively long distance and incapable of reaching each other,
this solution is relatively feasible. However, if two sides of
communication are relatively close to each other within a
communication scope of the other side, transmitting a packet
between the terminals directly without the need to be forwarded by
a base station can save half of resources.
Direct communication between a device and a device (D2D
communication for short, Device to Device) enables direct
communication between terminal devices without requiring any
intermediate infrastructure. Therefore, the direct communication
between terminal devices can use spectrum resources more
efficiently, increase a capacity of a cellular network, and reduce
overheads of control signaling of a base station, and is a
technology that can bring enormous benefits to cellular network
communications. Because the D2D communication is direct
communication between terminals, a paging message needs to be
directly sent from a paging terminal to a paged terminal without
requiring assistance of the base station or a core network. Some
conventional technologies can implement D2D communication, such as
wifi, BT, and ad hoc. However, these systems all work in
asynchronous mode. Therefore, in a D2D communications system in the
prior art, system devices all work in asynchronous mode, and as a
result a UE cannot effectively discover other UEs in a process of
mutual discovery of D2D user equipments (User Equipment, UE),
wasting system power.
SUMMARY
A purpose of embodiments of the present invention is to provide a
D2D device discovery method based on an LTE cellular communications
system, so as to improve system efficiency of a D2D communications
system to some extent.
To achieve the foregoing purpose, the embodiments of the present
invention provide the following technical solutions:
An embodiment of the present invention is implemented as follows: a
D2D device discovery method based on a Long Term Evolution LTE
cellular communications system, where the method includes:
acquiring, by a first D2D UE, timing information of the first D2D
UE from the LTE cellular communications system;
receiving, by the first D2D UE in a discovery subframe, a device
discovery signal from a second D2D UE according to the timing
information, and the device discovery signal includes a pilot
orthogonal frequency division multiplexing (Orthogonal Frequency
Division Multiplexing, OFDM) symbol and a device information OFDM
symbol; and
acquiring, by the first D2D UE, an arrival time of the device
discovery signal sent by the second D2D UE by performing a time
domain correlation of the pilot OFDM symbol of the device discovery
signal received in the discovery subframe and a local pilot
sequence, and acquiring device information of the second D2D UE by
parsing the device information OFDM symbol of the device discovery
signal received in the discovery subframe, so as to discover the
second D2D UE by the first D2D UE.
An embodiment of the present invention further provides a D2D
device discovery apparatus based on a Long Term Evolution LTE
cellular communications system, where the system includes:
an acquiring unit, configured for a first D2D UE to acquire timing
information of the first D2D UE from the LTE cellular
communications system;
a receiving unit, configured for the first D2D UE to receive, in a
discovery subframe, a device discovery signal from a second D2D UE
according to the timing information, and the device discovery
signal includes a pilot orthogonal frequency division multiplexing
OFDM symbol and a device information OFDM symbol; and
a discovering unit, configured for the first D2D UE to: acquire an
arrival time of the device discovery signal sent by the second D2D
UE by performing a time domain correlation of the pilot OFDM symbol
of the device discovery signal received in the discovery subframe
and a local pilot sequence, and acquire device information of the
second D2D UE by parsing the device information OFDM symbol of the
device discovery signal received in the discovery subframe, so as
to discover the second D2D UE by the first D2D UE.
Compared with the prior art, the embodiments of the present
invention have the following beneficial effects: from an LTE
cellular communications system, a first D2D UE acquires timing
information of the first D2D UE, and receives, in a discovery
subframe, a device discovery signal according to the timing
information, where the device discovery signal is sent by a second
D2D UE in the discovery subframe, and acquires an arrival time of
the device discovery signal sent by the second D2D UE and device
information of the second device according to the received
discovery signal, thereby implementing D2D communication in an LTE
cellular network system. In a synchronous communications system,
the D2D UE may, in each discovery subframe, send a device discovery
signal or monitor a device discovery signal sent by other devices.
When one of two D2D UEs sends and the other D2D UE receives a
device discovery signal in a same discovery subframe, device
discovery can be implemented, thereby shortening a time of
discovery between the D2D UEs, and enabling one D2D UE to
effectively discover other D2D UEs. This improves system
efficiency, and saves power of the D2D UE. In addition, due to
compatibility with the LTE cellular network system, it is
beneficial to implementation of D2D communication in a cellular
network.
BRIEF DESCRIPTION OF THE DRAWINGS
To describe the technical solutions in the embodiments of the
present invention more clearly, the following briefly introduces
the accompanying drawings required for describing the embodiments.
Apparently, the accompanying drawings in the following description
show merely some embodiments of the present invention, and a person
of ordinary skill in the art may still derive other drawings from
these accompanying drawings without creative efforts.
FIG. 1 is a schematic diagram of network deployment of a D2D device
discovery system based on an LTE cellular communications system
according to Embodiment 1 of the present invention;
FIG. 2 is a schematic flowchart of implementing a D2D device
discovery method based on an LTE cellular communications system
according to Embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of a timing structure of a D2D
communications network according to Embodiment 2 of the present
invention;
FIG. 4 is a schematic diagram of receiving and sending a D2D device
discovery signal by means of uplink timing according to Embodiment
4 of the present invention;
FIG. 5 is a schematic diagram of receiving and sending a D2D device
discovery signal by means of downlink timing according to
Embodiment 4 of the present invention;
FIG. 6 is a schematic diagram of a timing structure of a discovery
subframe according to Embodiment 5 of the present invention;
FIG. 7 is a schematic diagram of a maximum time difference of a
device discovery signal according to Embodiment 5 of the present
invention;
FIG. 8 is a schematic diagram of a maximum delay of a device
discovery signal according to Embodiment 5 of the present
invention;
FIG. 9 is a structural diagram of time frequency of a discovery
subframe according to Embodiment 6 of the present invention;
FIG. 10 is a structural diagram of time frequency of another
discovery subframe according to Embodiment 6 of the present
invention;
FIG. 11 is a structural diagram of time frequency of yet another
discovery subframe according to Embodiment 6 of the present
invention;
FIG. 12 is a schematic structural diagram of a D2D device discovery
apparatus based on a Long Term Evolution LTE cellular
communications system according to Embodiment 7 of the present
invention; and
FIG. 13 is a schematic structural diagram of a D2D device discovery
apparatus based on a Long Term Evolution LTE cellular
communications system according to Embodiment 8 of the present
invention.
DETAILED DESCRIPTION
To make objectives, technical solutions and advantages of the
present invention clearer, the following describes the present
invention in further detail with reference to accompanying drawings
and embodiments. It should be understood that the specific
embodiments described herein are merely for explaining the present
invention, and are not intended to limit the present invention.
An embodiment of the present invention provides a D2D device
discovery method based on a Long Term Evolution LTE cellular
communications system, where the method includes:
acquiring, by a first D2D UE, timing information of the first D2D
UE from the LTE cellular communications system;
receiving, by the first D2D UE in a discovery subframe, a device
discovery signal from a second D2D UE according to the timing
information, and the device discovery signal includes a pilot
orthogonal frequency division multiplexing OFDM symbol and a device
information OFDM symbol; and
acquiring, by the first D2D UE, an arrival time of the device
discovery signal sent by the second D2D UE by performing a time
domain correlation of the pilot OFDM symbol of the device discovery
signal received in the discovery subframe and a local pilot
sequence, and acquiring device information of the second D2D UE by
parsing the device information OFDM symbol of the device discovery
signal received in the discovery subframe, so as to discover the
second D2D UE by the first D2D UE.
An embodiment of the present invention further provides a D2D
device discovery apparatus based on a Long Term Evolution LTE
cellular communications system, where the system includes:
an acquiring unit, configured for a first D2D UE to acquire timing
information of the first D2D UE from the LTE cellular
communications system;
a receiving unit, configured for the first D2D UE to receive, in a
discovery subframe, a device discovery signal from a second D2D UE
according to the timing information, and the device discovery
signal includes a pilot orthogonal frequency division multiplexing
OFDM symbol and a device information OFDM symbol; and
a discovering unit, configured for the first D2D UE to: acquire an
arrival time of the device discovery signal sent by the second D2D
UE by performing a time domain correlation of the pilot OFDM symbol
of the device discovery signal received in the discovery subframe
and a local pilot sequence, and acquire device info Ration of the
second D2D UE by parsing the device information OFDM symbol of the
device discovery signal received in the discovery subframe, so as
to discover the second D2D UE by the first D2D UE. The following
describes the implementation of the present invention in detail
with reference to specific embodiments:
Embodiment 1
FIG. 1 shows a schematic diagram of network deployment of a D2D
device discovery system based on an LTE cellular communications
system according to Embodiment 1 of the present invention. The
system includes a plurality of D2D UEs, and a process in which
device discovery is implemented between the D2D UE devices and
based on an LTE cellular communications system is as follows: Each
D2D UE acquires its own timing from the LTE cellular system; sends,
in a discovery subframe, a device discovery signal; and receives,
in the discovery subframe, device discovery signals of other D2D
UEs, where the device discovery signal includes a pilot OFDM symbol
and a device information OFDM symbol, so that device discovery is
implemented between the D2D UEs; and basic information and timing
of an adjacent D2D UE are acquired, so that mutual discovery is
implemented between the D2D UE devices. Using a first D2D UE 11 and
a second D2D UE 12 as an example, a process in which device
discovery is implemented between the first D2D UE 11 and the second
D2D UE 12 and based on an LTE cellular communications system is as
follows: the first D2D UE sends, in a discovery subframe, a device
discovery signal according to uplink timing (or downlink timing) of
the first D2D UE, the second D2D UE device receives, in the
discovery subframe, the device discovery signal according to uplink
timing (or downlink timing) of the second D2D UE, where the device
discovery signal is sent by the first D2D UE, and the second D2D UE
performs a time domain correlation according to a pilot OFDM symbol
and a device information OFDM symbol of the first D2D UE to acquire
an arrival time of the device discovery signal sent by the first
D2D UE, where the device discovery signal is sent by the first D2D
UE, to acquire device information of the first D2D UE by parsing.
In this way, the second D2D UE discovers the first D2D UE.
Similarly, the first D2D UE can discover the second D2D UE. The
following gives description by using an embodiment.
FIG. 2 shows a flowchart of implementing a D2D device discovery
method based on an LTE cellular communications system according to
Embodiment 1 of the present invention, as detailed below:
In S201, A first D2D UE acquires timing information of the first
D2D UE from the LTE cellular communications system.
In this embodiment, the D2D UE may acquire timing information of
the first D2D UE from synchronization information of a cell, where
the timing information is a time at which a signal is sent or
received.
In S202, the first D2D UE receives, in a discovery subframe, a
device discovery signal from a second D2D UE according to the
timing information, and the device discovery signal includes a
pilot OFDM symbol and a device information OFDM symbol.
In this embodiment, the first D2D UE receives, in the discovery
subframe, the device discovery signal according to the timing
information and according to a timing structure, where the device
discovery signal is sent by the second D2D UE in the discovery
subframe, and the timing structure includes the discovery
subframe.
In this embodiment, the device discovery signal includes a device
information OFDM symbol and a pilot OFDM symbol, and the device
information OFDM symbol is used to carry basic information of a
device, such as a device ID and a device type; and the pilot OFDM
symbol is used for synchronization and channel estimation.
In S203, the first D2D UE acquires an arrival time of the device
discovery signal sent by the second D2D UE by performing a time
domain correlation of the pilot OFDM symbol of the device discovery
signal received in the discovery subframe and a local pilot
sequence, parses the device information OFDM symbol of the device
discovery signal received in the discovery subframe, to acquire
device information of the second D2D UE, thereby discovering the
second D2D UE.
In this embodiment, the first D2D UE and the second D2D UE may be
in a sleep state for a long time, and need to wake up only when a
device discovery signal is sent or received, thereby effectively
saving power of the D2D UE.
In this embodiment, a time at which a signal is sent to the second
D2D UE is calculated according to the acquired arrival time of the
device discovery signal sent by the second D2D UE and the device
information of the second device, thereby providing a condition for
further paging and communication between the D2D UEs.
In this embodiment, from an LTE cellular communications system, a
first D2D UE acquires timing information of the first D2D UE, and
receives, in a discovery subframe, a device discovery signal
according to the timing information, where the device discovery
signal is sent by a second D2D UE, and acquires an arrival time of
the device discovery signal sent by the second D2D UE and device
information of the second device according to the device discovery
signal received in the discovery subframe, thereby implementing D2D
communication in an LTE cellular network system. In a synchronous
communications system, the D2D UE may, in each discovery subframe,
send a device discovery signal or monitor a device discovery signal
sent by other devices. When one of two D2D UEs sends and the other
D2D UE receives a device discovery signal in a same discovery
subframe, device discovery can be implemented, thereby shortening a
time of discovery between the D2D UEs, and enabling one D2D UE to
effectively discover other D2D UEs. This improves system
efficiency, and saves power of the D2D UE. In addition, due to
compatibility with the LTE cellular network system, it is
beneficial to implementation of D2D communication in a cellular
network.
Embodiment 2
In this embodiment, in a D2D device discovery process, a timing
structure of a D2D communications network may be similar to a
timing structure of an LTE cellular network. As shown in FIG. 3,
similar to the LTE timing structure, each subframe is 1 ms in
length and consist of two timeslots of 0.5 millisecond, and each
timeslot consist of six (extended cyclic prefix (cyclic prefix,
CP)) or seven (normal CP) OFDM symbols. Every 10 subframes form a
10 ms radio frame. According to functions, each subframe may be a
discovery subframe, a paging subframe or a communication
subframe.
In this embodiment, the discovery subframe is primarily used for
device recovery. It carries information such as a pilot, a device
identifier, a device type, and a service provided by a device. Each
D2D UE discovers other adjacent D2D UEs and their device
information by using the discovery subframe, thereby providing a
condition for further D2D communication.
It is unnecessary that each radio frame includes the discovery
subframe. As shown in FIG. 3, at intervals of T radio frames, one
radio frame includes the discovery subframe, where T=1, . . . , t,
a value of t depends on power saving of the UE and load of cellular
UEs and D2D UEs in a cell. When there are a relatively large number
of D2D UEs, a value of t may be increased; when there are a
relatively small number of D2D UEs, a value of t may be decreased.
In addition, the value of t may be notified, by an evolved Node B
(evolved Node B, eNB) to perform dynamic or semi-static
configuration, to all D2D UEs by means of broadcasting.
In this embodiment, to avoid interference between cellular
communication and D2D communication, a cellular resource scheduling
center (base station) may further schedule cellular communication
at a position different from a discovery subframe location.
In this embodiment, the discovery subframe includes a plurality of
OFDM symbols. For example, the discovery subframe may include 12
OFDM symbols or 14 OFDM symbols, which are pilot OFDM symbols and
device information OFDM symbols. Each of the OFDM symbols is
divided into M frequency resource elements in a frequency domain,
where M is an integer greater than or equal to 1. Each frequency
resource element includes several subcarriers. Further, one or more
frequency resource elements of each OFDM symbol serve as a device
discovery resource element, and one or more of the device discovery
resource elements are selected by each D2D UE as a carrier for a
device discovery signal of the each D2D UE. Specifically, each D2D
UE sends the device discovery signal on several device discovery
resource elements of the discovery subframe, and each D2D UE
receives device discovery signals of other D2D UEs on all the
device discovery resource elements of the discovery subframe.
In addition, the paging subframe is primarily used for direct
paging between the D2D UEs, and is primarily used to carry a device
identifier of a paging destination UE, and further, may carry a
paging source communications device identifier, so that the paging
destination UE confirms a paging source and sends paging response
information, and may further carry information such as
communication frequency resources and power of a communication
subframe to help create a communication link between two sides of
communication, that is, the paging source and the paging
destination UE, and provide a guarantee for next-step data
transmission. The paging subframe immediately follows the discovery
subframe, which is considered based on two factors: First, such a
practice can improve communication efficiency, and the UE can page
a UE immediately after discovering the UE it wants to communicate
with in the discovery subframe, so as to create a communication
link and begin communication instead of waiting for the paging
subframe for a further long time before paging, thereby reducing a
delay and improving communication quality; and, second, such a
practice is beneficial to a consideration of power saving of the UE
and avoids frequently waking up the UE.
Communication subframes are subframes that have the largest
quantity, and are primarily used for data transmission, thereby
improving a D2D data transmission rate significantly.
Embodiment 3
A D2D device discovery method based on an LTE cellular
communications system according to an embodiment of the present
invention may further include: sending, by the first D2D UE, a
device discovery signal to the second D2D UE in the discovery
subframe according to the timing information, so that the second
D2D UE receives, in the discovery subframe, the device discovery
signal sent by the first D2D UE, performs a time domain correlation
of a pilot OFDM symbol of the device discovery signal received in
the discovery subframe and a local pilot sequence, to acquire an
arrival time of the device discovery signal sent by the first D2D
UE, parses a device information OFDM symbol of the device discovery
signal received in the discovery subframe, to acquire device
information of the first D2D UE, so that the second D2D UE
discovers the first D2D UE. This step may be performed before the
first D2D UE performs device discovery of the second D2D UE, or
after the first D2D UE performs device discovery of the second D2D
UE.
In this embodiment, a first D2D UE sends a device discovery signal
to a second D2D UE in a discovery subframe according to timing
information, so that the second D2D UE discovers a device of the
first D2D UE according to the device discovery signal sent by the
first D2D UE. This process shortens a time of discovery between the
D2D UEs, enables one D2D UE to effectively discover other D2D UEs,
improves system efficiency, and saves power of the D2D UE.
Embodiment 4
In this embodiment, timing information is uplink timing or downlink
timing, and therefore:
the receiving, in Embodiment 1 by the first D2D UE in a discovery
subframe, a device discovery signal from a second D2D UE according
to the timing information, is: receiving, by the first D2D UE in
the discovery subframe, the device discovery signal from a second
D2D UE according to the uplink timing or the downlink timing of the
first D2D UE, where the device discovery signal is sent by the
second D2D UE;
the sending, in Embodiment 3 by the first D2D UE, a device
discovery signal to the second D2D UE in the discovery subframe
according to the timing information is: sending, by the first D2D
UE, the device discovery signal to the second D2D UE in the
discovery subframe according to the uplink timing or the downlink
timing of the first D2D UE.
The following describes principles of implementing the receiving,
by the first D2D UE in the discovery subframe, the device discovery
signal by means of uplink timing or downlink timing of the first
D2D UE, where the device discovery signal is sent by the second D2D
UE and the sending, by the first D2D UE, the device discovery
signal to the second D2D UE in the discovery subframe by means of
uplink timing or downlink timing of the first D2D UE:
for a scenario in which the first D2D UE receives, in the discovery
subframe, the device discovery signal by means of uplink timing of
the first D2D UE, where the device discovery signal is sent by the
second D2D UE, and the first D2D UE sends, in the discovery
subframe, the device discovery signal to the second D2D UE by means
of uplink timing of the first D2D UE, refer to FIG. 4, which is a
schematic diagram of sending and receiving a D2D device discovery
signal by means of uplink timing, where the left diagram shows a
timing relationship between D2D UEs, and the right diagram shows a
location relationship between D2D UEs. It is assumed that D2D_UE 1
is a D2D UE that sends a device discovery signal, and D2D_UE 2 is a
D2D UE that receives device discovery signals of other D2D UEs. The
D2D_UE 1 sends the device discovery signal by means of uplink
timing of the first D2D UE T.sub.1; and, at the same time, the
D2D_UE 2 receives the device discovery signal of the D2D_UE 1 by
means of uplink timing of the second D2D UE T.sub.2. The device
discovery signal of the D2D_UE 1 arrives at the D2D_UE 2 at time
T'.sub.1, as shown in the left diagram of FIG. 4, where T.sub.B is
eNB timing. Because
.DELTA.T=T.sub.2-T.sub.1=(T.sub.B-T.sub.1)-(T.sub.B-T.sub.2),
T.sub.B-T.sub.1 may serve as a distance between the D2D_UE 1 and an
eNB, and T.sub.B-T.sub.2 may serve as a distance between the D2D_UE
2 and the eNB. Similarly, T'.sub.1-T.sub.1 may serve as a distance
between the D2D_UE 1 and the D2D_UE 2. Then according to location
relationships between the D2D_UE 1, the D2D_UE 2, and the eNB, it
can be learned that
(T.sub.B-T.sub.1)-(T.sub.B-T.sub.1).ltoreq.T'.sub.1-T.sub.1, and
that a time at which the device discovery signal of the D2D_UE 1
arrives at the D2D_UE 2 is definitely after the time T.sub.2 at
which the device discovery signals of other D2D UE devices are
received by the D2D_UE 2. In this way, the device discovery signals
of other D2D UE devices can be received completely, and
interference between discovery subframe signals of different D2D
UEs and interference on uplink signals of other cellular UEs can be
avoided effectively.
For a scenario in which the first D2D UE receives, in the discovery
subframe, the device discovery signal by means of downlink timing
of the first D2D UE, where the device discovery signal is sent by
the second D2D UE, and the first D2D UE sends, in the discovery
subframe, the device discovery signal to the second D2D UE by means
of downlink timing of the first D2D UE, refer to FIG. 5, which is a
schematic diagram of sending and receiving a D2D discovery subframe
signal by means of downlink timing, where the left diagram shows a
timing relationship between D2D UEs, and the right diagram shows a
location relationship between D2D UEs. It is assumed that D2D_UE 1
is a D2D UE that sends a device discovery signal, and D2D_UE 2 is a
D2D UE that receives device discovery signals of other D2D UEs. The
D2D_UE 1 sends the device discovery signal by means of downlink
timing of the first D2D UE T.sub.1; and, at the same time, the
D2D_UE 2 receives the device discovery signal of the D2D_UE 1 by
means of downlink timing of the second D2D_UE 2 T.sub.2. The device
discovery signal of the D2D_UE 1 arrives at the D2D_UE 2 at time
T'.sub.1, as shown in the left diagram of FIG. 5, where T.sub.B is
eNB timing. Because
.DELTA.T=T.sub.2-T.sub.1=(T.sub.2-T.sub.B)-(T.sub.1-T.sub.B)
T.sub.1-T.sub.B may serve as a distance between the D2D_UE 1 and an
eNB, and T.sub.2-T.sub.B may serve as a distance between the D2D_UE
2 and the eNB. Similarly, T'.sub.1-T.sub.1 may serve as a distance
between the D2D_UE 1 and the D2D_UE 2. Then according to location
relationships between the D2D_UE 1, the D2D_UE 2, and the eNB, it
can be learned that
(T.sub.2-T.sub.B)-(T.sub.1-T.sub.B).ltoreq.T'.sub.1-T.sub.1, and
that a time at which the device discovery signal of the D2D_UE 1
arrives at the D2D_UE 2 is definitely after the time T.sub.2 at
which the device discovery signals of other D2D UE devices are
received by the D2D_UE 2. In this way, the device discovery signals
of other D2D UE devices can be received completely, and
interference between device discovery signals of different D2D UEs
and interference on uplink signals of other cellular UEs can be
avoided effectively.
In this embodiment, on several device discovery resource elements
of a discovery subframe, a D2D UE sends a device discovery signal
by means of its own uplink timing or downlink timing, or receives
device discovery signals of other D2D UEs by means of its own
uplink timing or downlink timing. Therefore, when sending or
receiving the device discovery signal, each D2D UE can separate the
device discovery signals of different UEs in a time domain and a
frequency domain, thereby avoiding a discovery conflict between D2D
UEs, improving a success ratio of device discovery, and improving
discovery efficiency.
Embodiment 5
In this embodiment, the discovery subframe includes a plurality of
OFDM symbols, and each OFDM symbol includes a cyclic prefix (Cyclic
Prefix, CP), and a length of the CP may be determined in the
following manner:
1. A guard interval (Gard Interval, GI) is added to the discovery
subframe, where the GI is located between the discovery subframe
and an adjacent paging subframe following the discovery subframe,
and the length of the CP of the discovery subframe is determined
according to the GI; or
2. Both the discovery subframe and an adjacent paging subframe
following the discovery subframe use normal CPs; or
3. Both the discovery subframe and an adjacent paging subframe
following the discovery subframe use extended CPs.
To meet requirements in a D2D device discovery scenario, it is
necessary to determine the length of the CP of the discovery
subframe signal, and determine a device discovery distance
according to the length of the CP. Primarily the following two
requirements are considered for the length of the CP and the device
discovery distance:
First, a maximum difference of a time when discovery subframe
signals from a plurality of D2D UEs that sends device discovery
signals arrive at a same D2D UE that receives the device discovery
signals cannot be greater than a length of a CP, so as to avoid
inter-carrier interference caused by damage to carrier
orthogonality between different D2D UEs.
Second, a maximum delay extension of the last OFDM symbol of the
discovery subframe cannot interfere with the first OFDM symbol of a
subsequent paging subframe signal, so as to avoid intersymbol
interference.
The following describes the foregoing three methods of determining
a length of a CP:
1. A guard interval GI is added to the discovery subframe, where
the GI is located between the discovery subframe and an adjacent
paging subframe following the discovery subframe, and the length of
the CP of the discovery subframe is determined according to the GI.
FIG. 6 is a schematic diagram of a timing structure of a discovery
subframe. A guard interval (GI) is added between the discovery
subframe and a subsequent paging subframe. In this case, the length
of the CP is 15.625 us, and, for a 20 M bandwidth, is 480 Ts; and
the length of the GI is 12.5 us, and, for a 20 M bandwidth, is 384
Ts. The subsequent paging subframe is a normal CP. When this frame
format is used, the maximum device discovery distance is 1.5625
km.
First, considering a requirement of a first aspect, the maximum
difference of a time when device discovery signals from a plurality
of D2D UEs that sends the device discovery signals arrive at a same
D2D UE that receives the device discovery signals is calculated.
FIG. 7 is a schematic diagram of the maximum time difference of
device discovery signals, where the left diagram shows a timing
relationship of the device discovery signals, and the right diagram
shows a location relationship between D2D UEs. D2D_UE 1 sends a
device discovery signal at its uplink timing T.sub.1, D2D_UE 2
sends a device discovery signal at its uplink timing T.sub.2, and a
D2D_UE 3 receives the device discovery signals of the D2D_UE 1 and
the D2D_UE 2 at its uplink timing T.sub.3. The D2D_UE 3 receives
the device discovery signal of the D2D_UE 1 at time T'.sub.1, and
receives the device discovery signal of the D2D_UE 2 at time
T'.sub.2. The device discovery signal delay of the D2D_UE 2 is
extended to T''.sub.2, that is, the delay is extended to
T.sub.d=T''.sub.2-T'.sub.2. It is generally deemed that T.sub.d is
equal to a propagation time of a signal. Therefore, a difference of
a time at which the two device discovery signals arrive at the
D2D_UE 3 is:
.DELTA.T=|T''.sub.2-T'.sub.1|=|T'.sub.2+T.sub.d-T'.sub.1|=|T.sub.2+T.sub.-
23)-(T.sub.1+T.sub.13)+T.sub.d|=|(T.sub.2-T.sub.1)+(T.sub.23-T.sub.13)+T.s-
ub.d|.ltoreq.|T.sub.2-T.sub.1|+|T.sub.23-T.sub.13|+T.sub.d.ltoreq.2T.sub.1-
2+T.sub.d
As can be learned that, when and only when
(T.sub.2-T.sub.1)(T.sub.23-T.sub.13)>0 and
|T.sub.2-T.sub.1|=T.sub.12, |T.sub.23-T.sub.13|=T.sub.12, the equal
sign is justified, where T.sub.12 is a time at which the signal
from the D2D_UE 1 arrives at the D2D_UE 2, T.sub.23 is a time at
which the signal from the D2D_UE 2 arrives at the D2D_UE 3, and
T.sub.13 is a time at which the signal from the D2D_UE 1 arrives at
the D2D_UE 3. From the foregoing analysis, it can be learned that
when the D2D_UE 1 coincides with the D2D_UE 3 and the D2D_UE 2 is
between the D2D_UE 1 and the eNB and they form a straight line, the
difference of a time at which the device discovery signals of the
D2D_UE 1 and the D2D_UE 2 arrive at the D2D_UE 3 is the largest. In
this case, T.sub.d=T.sub.12, and the maximum delay difference is
.DELTA.T.sub.max=3T.sub.12. In addition, to avoid intersymbol
interference and inter-carrier interference of the discovery
subframe, the length T.sub.CP,dis of the CP of the discovery
subframe needs to meet the following:
T.sub.CP,dis.gtoreq.3T.sub.12.
The following considers a requirement of a second aspect and
calculates the maximum impact caused by extension of the delay of
the discovery subframe on a subsequent paging subframe. FIG. 8 is a
schematic diagram of a maximum delay of device discovery signals,
where the left diagram shows a timing relationship of the device
discovery signals, and the right diagram shows a location
relationship between D2D UEs. D2D_UE 2 sends a device discovery
signal at its uplink timing T.sub.2, and D2D_UE 1 receives a device
discovery signal of the D2D_UE 2 at its uplink timing T.sub.1.
Subsequently, the D2D_UE 1 receives the device discovery signal of
the D2D_UE 2 at time T'.sub.2, and the device discovery signal
delay of the D2D_UE 2 is extended to T''.sub.2, that is, the delay
is extended to T.sub.d=T''.sub.2-T'.sub.2. It is generally deemed
that T.sub.d is equal to a propagation time of a signal. Therefore,
a delay difference of a time at which the device discovery signals
of the D2D_UE 2 arrive at the D2D_UE 1 is:
.DELTA.T=|T'.sub.2-T.sub.1+T.sub.d|=|T.sub.2+T.sub.12-T.sub.1+T.sub.d|.lt-
oreq.|T.sub.2-T.sub.1|+T.sub.12+T.sub.d.gtoreq.2T.sub.12+T.sub.d
As can be learned that, when and only when
T.sub.2-T.sub.1=T.sub.12, the equal sign is justified, where
T.sub.12 is a transmission time of the signal from the D2D_UE 2 to
the D2D_UE 1. In this case, T.sub.d=T.sub.12, and the maximum delay
time is .DELTA.T.sub.max=3T.sub.12. In this case, a guard interval
is added between the discovery subframe and a subsequent paging
subframe to avoid intersymbol interference caused by the last OFDM
symbol of the discovery subframe on the first OFDM symbol of the
subsequent paging subframe. A length of the guard interval needs to
meet the following: T.sub.GI+T.sub.CP,normal.gtoreq.3T.sub.12,
where T.sub.CP,normal is a length of a normal CP. According to the
foregoing analysis, a length of the CP, the length of the guard
interval, and a maximum device discovery distance may be calculated
by using the following equation set:
.times..times. ##EQU00001##
Therefore, it is calculated that the length of the CP of the
discovery subframe is 15.78 us, and, for a 20 M bandwidth, is 485
Ts; and the length of the GI is 10.55 us, and, for a 20 M
bandwidth, is 324 Ts. Because the number of sampling points of the
CP is preferably an integer multiple of 16, the length of the CP
may be set to 15.625 us, and, for a 20 M bandwidth, to 480 Ts; and
the length of the GI is 12.5 us, and, for a 20 M bandwidth, is 384
Ts. The maximum device discovery distance is 1.5625 km.
2. Both the discovery subframe and an adjacent paging subframe
following the discovery subframe are normal CPs (normal CP). The
length of the normal CP is 4.96 us, and for a 20 M bandwidth, is
144 Ts. By using the normal CP, the two requirements of D2D device
discovery can also be met. For details, deducing may be performed
by referring to the manner in method 1, and no repeated description
is given here. In this case, the longest device discovery distance
is 469 m.
3. Both the discovery subframe and an adjacent paging subframe
following the discovery subframe are extended CPs (extended CP).
The length of the extended CP is 16.67 us, and for a 20 M
bandwidth, is 512 Ts. By using the extended CP, the requirements of
the two aspects of the D2D device discovery can also be met. For
details, deducing may be performed by referring to the manner in
method 1, and no repeated description is given here. In this case,
the longest device discovery distance is 1.66 km.
It is noteworthy that the normal CP and the extended CP in method 2
and method 3 are two CP lengths that are generally used in an LTE
communications system, and are common knowledge for a person
skilled in the art.
In this embodiment, the discovery subframe uses a CP of an
appropriate length, for example, by adding a guard interval between
the discovery subframe and the paging subframe, so as to
effectively avoid interference between the device discovery signals
of D2D UEs.
Embodiment 6
In this embodiment, the discovery subframe includes a plurality of
OFDM symbols, and a frame structure of the discovery subframe may
use the following manner: in a plurality of OFDM symbols of the
discovery subframe, at least two OFDM symbols are selected as one
group, each group includes one pilot OFDM symbol and at least one
device information OFDM symbol, and, when the number of OFDM
symbols included in each group is greater than 2, the pilot OFDM
symbol is located in a non-edge location in each group, where pilot
sequences on different device discovery resource elements of the
discovery subframe are orthogonal.
Specifically, when the discovery subframe includes 12 OFDM symbols,
the frame structure of the discovery subframe is:
every two of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
pilot OFDM symbol and the second symbol is a device information
OFDM symbol; or
every two of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
device information OFDM symbol and the second symbol is a pilot
OFDM symbol; or
every three of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol and
the third symbol are device information OFDM symbols and the second
symbol is a pilot OFDM symbol; or
every four of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the second symbol is a
pilot OFDM symbol and the first symbol, the third symbol and the
fourth symbol are device information OFDM symbols; or
every four of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the third symbol is a
pilot OFDM symbol and the first symbol, the second symbol and the
fourth symbol are device information OFDM symbols.
For ease of understanding, an implementation example is used as
follows to describe time-frequency resource structure design of the
discovery subframe:
FIG. 9 shows a structural diagram of time frequency of a discovery
subframe signal. Each OFDM symbol of the discovery subframe is
divided into a plurality of device discovery resource elements in a
frequency domain. Every two of the 12 OFDM symbols of the discovery
subframe are divided into one group, and, in each group, the first
symbol is a pilot OFDM symbol and the second symbol is a device
information OFDM symbol. A pilot OFDM symbol alternates with a
device information OFDM symbol in distribution. The pilot OFDM
symbol is primarily used for synchronization and channel
estimation, and the device information OFDM symbol primarily
carries basic information (such as a device ID) of a device. From
one or more groups of pilot OFDM symbols and device information
OFDM symbols, each D2D UE selects one or more device discovery
resource elements to send pilot and device information.
FIG. 10 shows a structural diagram of time frequency of another
discovery subframe signal. Every three of the 12 OFDM symbols of
the discovery subframe are divided into one group, and, in each
group, the first symbol and the third symbol are device information
OFDM symbols and the second symbol is a pilot OFDM symbol.
FIG. 11 shows a structural diagram of time frequency of yet another
discovery subframe signal. Every four of the 12 OFDM symbols of the
discovery subframe are divided into one group, and, in each group,
the second symbol is a pilot OFDM symbol and the first symbol, the
third symbol and the fourth symbol are device information OFDM
symbols.
Similarly, when the discovery subframe includes 14 OFDM symbols,
the frame structure of the discovery subframe is:
every two of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
pilot OFDM symbol and the second symbol is a device information
OFDM symbol; or
every two of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
device information OFDM symbol and the second symbol is a pilot
OFDM symbol; or
every seven of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, any one symbol among
the second symbol to the sixth symbol is a pilot OFDM symbol and
other six OFDM symbols are device information OFDM symbols.
Embodiment 7
FIG. 12 shows a schematic structural diagram of a D2D device
discovery apparatus based on a Long Term Evolution LTE cellular
communications system according to Embodiment 7 of the present
invention. For ease of description, only parts related to this
embodiment of the present invention are shown.
The D2D device discovery apparatus may include an acquiring unit
121, a receiving unit 122, and a discovering unit 123.
The acquiring unit 121 is configured for a first D2D UE to acquire
timing information of the first D2D UE from the LTE cellular
communications system.
The receiving unit 122 is configured for the first D2D UE to
receive, in a discovery subframe, a device discovery signal from a
second D2D UE according to the timing information, and the device
discovery signal includes a pilot orthogonal frequency division
multiplexing OFDM symbol and a device information OFDM symbol.
The discovering unit 123 is configured for the first D2D UE to
acquire an arrival time of the device discovery signal sent by the
second D2D UE by performing a time domain correlation of the pilot
OFDM symbol of the device discovery signal received in the
discovery subframe and a local pilot sequence, parse the device
information OFDM symbol of the device discovery signal received in
the discovery subframe, to acquire device information of the second
D2D UE, so that the first D2D UE discovers the second D2D UE.
In this embodiment, each OFDM symbol of the discovery subframe
signal is divided into M frequency resource elements in a frequency
domain, one or more frequency resource elements of each OFDM symbol
serve as a device discovery resource element, and one or more of
the device discovery resource elements are selected by each D2D UE
as a carrier for a device discovery signal of the each D2D UE.
The D2D device discovery apparatus based on a Long Term Evolution
LTE cellular communications system according to this embodiment of
the present invention may be applied in the corresponding method
Embodiments 1 and 2. For details, refer to the description in
Embodiments 1 and 2, and no repeated description is given here.
Embodiment 8
On the D2D device discovery apparatus based on a Long Term
Evolution LTE cellular communications system in Embodiment 7
further includes a sending unit. Refer to FIG. 13, which shows a
structural diagram of a D2D device discovery apparatus based on a
Long Term Evolution LTE cellular communications system according to
Embodiment 8 of the present invention. The system includes an
acquiring unit 131, a receiving unit 132, a discovering unit 133,
and a sending unit 134.
Differences between the present invention and Embodiment 7 are as
follows:
The sending unit 134 is configured for a first D2D UE to send a
device discovery signal to a second D2D UE in a discovery subframe
according to the timing information, so that the second D2D UE
receives, in the discovery subframe, the device discovery signal
sent by the first D2D UE, performs a time domain correlation of a
pilot OFDM symbol of the device discovery signal received in the
discovery subframe and a local pilot sequence, to acquire an
arrival time of the device discovery signal sent by the first D2D
UE, parses a device information OFDM symbol of the device discovery
signal received in the discovery subframe, to acquire device
information of the first D2D UE, so that the second D2D UE
discovers the first D2D UE.
Optionally, when the timing information is uplink timing or
downlink timing, the receiving unit 132 is configured for the first
D2D UE to receive, in the discovery subframe, the device discovery
signal according to the uplink timing or the downlink timing of the
first D2D UE, where the device discovery signal is sent by the
second D2D UE.
The sending unit 134 is configured for the first D2D UE to send the
device discovery signal to the second D2D UE in the discovery
subframe according to the uplink timing or the downlink timing of
the first D2D UE.
The D2D device discovery apparatus based on a Long Tezai Evolution
LTE cellular communications system according to the embodiment of
the present invention may be applied in the corresponding method
Embodiments 3 and 4. For details, refer to the description in
Embodiments 3 and 4, and no repeated description is given here.
Embodiment 9
In this embodiment, the discovery subframe includes a plurality of
OFDM symbols, and each OFDM symbol includes one CP, and a length of
the CP is as follows:
a guard interval GI is added to the discovery subframe, where the
GI is located between the discovery subframe and an adjacent paging
subframe following the discovery subframe, and the length of the CP
of the discovery subframe is determined according to the GI; or
both the discovery subframe and an adjacent paging subframe
following the discovery subframe use normal CPs; or
both the discovery subframe and an adjacent paging subframe
following the discovery subframe use extended CPs.
A structure of the CP provided in this embodiment of the present
invention may be applied in the corresponding method embodiment 5.
For details, refer to the description in Embodiment 5, and no
repeated description is given here.
Embodiment 10
The discovery subframe includes a plurality of OFDM symbols, and a
frame structure of the discovery subframe is:
In a plurality of OFDM symbols of the discovery subframe, at least
two OFDM symbols are selected as one group, each group includes one
pilot OFDM symbol and at least one device information OFDM symbol,
and, when the number of OFDM symbols included in each group is
greater than 2, the pilot OFDM symbol is located in a non-edge
location in each group,
where pilot sequences on different device discovery resource
elements on each OFDM of the discovery subframe are orthogonal.
Optionally, when the discovery subframe includes 12 OFDM symbols,
the frame structure of the discovery subframe is:
every two of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
pilot OFDM symbol and the second symbol is a device information
OFDM symbol; or
every two of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
device information OFDM symbol and the second symbol is a pilot
OFDM symbol; or
every three of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol and
the third symbol are device information OFDM symbols and the second
symbol is a pilot OFDM symbol; or
every four of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the second symbol is a
pilot OFDM symbol and the first symbol, the third symbol and the
fourth symbol are device information OFDM symbols; or
every four of the 12 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the third symbol is a
pilot OFDM symbol and the first symbol, the second symbol and the
fourth symbol are device information OFDM symbols.
When the discovery subframe includes 14 OFDM symbols, the frame
structure of the discovery subframe is:
every two of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
pilot OFDM symbol and the second symbol is a device information
OFDM symbol; or
every two of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, the first symbol is a
device information OFDM symbol and the second symbol is a pilot
OFDM symbol; or
every seven of the 14 OFDM symbols of the discovery subframe are
divided into one group, and, in each group, any one symbol among
the second symbol to the sixth symbol is a pilot OFDM symbol and
other six OFDM symbols are device information OFDM symbols.
The structure of the discovery subframe provided in the embodiment
of the present invention may be applied in the corresponding method
embodiment 6. For details, refer to the description about
Embodiment 6 and no repeated description is given here.
Mutual reference may be made to a same or similar part between
embodiments in this specification. Each embodiment focuses on
differences from other embodiments, and the implementation process
described in each embodiment may be applied in other embodiments.
In particular, for an apparatus embodiment, the units included in
the apparatus embodiment are merely divided according to function
logic but are not limited to such division. Any division is
appropriate as long as it can implement the corresponding
functions. In addition, a specific name of each functional unit is
merely intended for mutual differentiation instead of limiting the
protection scope of the present invention. For an apparatus
embodiment, the apparatus embodiment is described briefly because
it is basically similar to the method embodiment, and, for related
parts, refer to a part of description of the method embodiment.
In addition, a person of ordinary skill in the art may understand
that, all or some of the steps of the methods of the embodiments
may be implemented by a program instructing related hardware. The
corresponding program may be stored in a computer-readable storage
medium, where the storage medium may be a medium capable of storing
program code, such as a USB flash drive, a removable hard disk, a
read-only memory (Read-Only Memory, ROM), a random access memory
(Random Access Memory, RAM), a magnetic disk, or an optical
disc.
The foregoing descriptions are merely exemplary embodiments of the
present invention, but are not intended to limit the present
invention. Any modifications, equivalent substitutions, and
improvements made within the spirit and principles of the present
invention shall fall within the protection scope of the present
invention.
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